Upright vacuum cleaners employ collection systems for separating and collecting contaminants from a working airstream for later disposal. Some collection systems can include a cyclone separator for separating contaminants from a working airstream and a removable dirt cup for receiving and collecting the separated contaminants from the cyclone separator. The cyclone separator can have a single cyclonic separation stage, or multiple stages. In another arrangement, the collection system can include an integrally-formed cyclone separator and dirt cup, with the dirt cup being provided with a bottom-opening dirt door for contaminant disposal. Other types of collection systems such as centrifugal separators or bulk separators use high-speed rotational motion of the air/debris to separate the dirt by centrifugal force.
Typically, working air enters and exits at an upper portion of the collection system, as the lower portion of the collection system is used to collect debris. Before exiting the collection system or passing to a downstream separation stage, the working air may flow through an exhaust grill. The exhaust grill can have openings through which air may pass. The openings may be defined by perforations or holes, or may be defined between spaced vanes or louvers. During operation, the openings of the exhaust grill may become blocked or clogged with debris, requiring periodic cleaning of the exhaust grill.